Changes over time Chapter 5 Life Science

Section 1 Notes Darwin’s Voyage

Charles Darwin Charles Robert Darwin (12 February 1809 – 19 April 1882) was an English naturalist. He established that all species of life have descended over time from common ancestry, and proposed the scientific theory that this branching pattern of evolution resulted from a process that he called natural selection.

Darwin’s Voyage Map Five Year Voyage

Darwin’s Sketches

Species A species is a group of similar organisms that can mate with each other and produce fertile offspring.

Similarities and Differences Darwin noticed that many organisms found on certain islands were similar to organisms found on the mainland.

Adaptation An adaptation is a trait that helps an organism survive and reproduce.

Adaptations

Theory of Evolution Darwin thought, the species gradually changed over many generations and became better adapted to the new conditions. The gradual change in a species over time is called evolution.

Scientific Theory A scientific theory is a well-tested concept that explains a wide range of observations.

Natural Selection Origin of Species explained Natural Selection Natural Selection is the process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

Nature selects who moves on and who doesn’t!!!!

Factors that affect the process of natural selection: Overpopulation Competition Variation Any difference between individuals of the same species is called a variation. Selection- Some variations make certain individuals better adapted to their environment. (They are selected by nature to live)

Role of Genes in Evolution Mutations cause the some organisms to gain a trait and adapt to their environment when compared to other species.

How do new species form? A new species might form when a group of individuals remain separated from the rest of its species long enough to evolve different traits.

Continental Drift Millions of years ago Earth’s landmasses were connected as one landmass. This land mass formed a supercontinent called Pangaea. Pangaea gradually split apart in a process called continental drift. As the continents separated, species became isolated from one another and began to evolve independently. Continent of Australia- Marsupials

Pangaea

The Fossil Record Section 2 Notes

What is a fossil? A fossil is the preserved remains or traces of an organism that lived in the past. A fossil can be formed from a bone, tooth, shell, or other part of an organism.

How do Fossils Form? Most fossils form when organisms that die become buried in sediments.

Sedimentary Rock When a river flows into a lake or ocean, the sediments carried by the river settle to the bottom. Layers of sediments build up and cover dead organisms. Over millions of years, the layers harden to become sedimentary rock.

Petrified Fossil Fossils that become buried in sediment actually change to rock. This is what we call a Petrified Fossil.

Molds A hollow space in sediment in the shape of an organism or part of an organism is called a mold.

Cast Sometimes a mold becomes filled in with hardened minerals, forming a cast.

Two ways to determine a fossil’s age? Relative Dating- technique used to determine which of two fossils is older. Absolute Dating- technique used to determine the actual age of a fossil. Radioactive elements- unstable elements that decay or break down. Half-life- time it takes for half of the atoms in a sample to decay.

Fossil Record Millions of fossils that scientists have collected are called the fossil record. Extinct- means no members of that species are still alive.

How fast does evolution occur? Gradualism- proposes that evolution occurs slowly but steadily. Punctuated equilibria- species evolve during short periods of rapid change.

Other evidence for Evolution Section 3 Notes

3 ways scientist study evidence for Evolution Body Structure Development before birth DNA sequence

Body Structure Homologous structure- similar structures that related species have inherited from a common ancestor.

Early Development Some organisms in early development look to be closely related to a common ancestor. Example p. 167 (Turtle, Chicken, and Rat)

Similarities in DNA DNA evidence provides scientists with new evidence about evolution when comparing organisms DNA sequence.

Watson and Crick The discovery in 1953 of the double helix, the twisted-ladder structure of deoxyribonucleic acid (DNA), by James Watson and Francis Crick.

Branching Tree A branching tree is a diagram that shows how scientists think different groups of organisms are related.